The Effect of Varus Deformity on Co-Activation of Abdominal and Lower Limb Muscles during Landing Task in Female Subjects

Research Article

Austin Sports Med. 2021; 6(1): 1046.

The Effect of Varus Deformity on Co-Activation of Abdominal and Lower Limb Muscles during Landing Task in Female Subjects

Azizi M¹, Azizi M²* and Khademi K¹

1Department of Physiotherapy, Shahid Beheshti University of Medical Sciences, Tehran, IRAN

2Biological and Environmental Sciences, University of Rhode Island, Kingston, USA

*Corresponding author: Mehri Azizi, Biological and Environmental Sciences, University of Rhode, Island, Kingston, USA

Received: April 27, 2021; Accepted: May 27, 2021; Published: June 03, 2021


Objective: Genuvarum deformity experience knee instability. This deformity can lead the patient to sever osteoarthritis. The recovery of postural stability is very important to prevention of these patients. Strategies aimed at stabilizing the muscle can have a long-term effect on the joint. This study was performed to determine the relationship between muscle stabilization strategies and knee instability, in order to determine how people with knee Genuvarum, respond to rapid absorption and muscle co- contraction during landing task.

Methods: Twenty female participants, (10 normal and 10 Genuvarum) in the present study. The subjects were land by preferred lower limb from a table (30 cm high) on a force plate. Vertical ground reaction force, time to peak of vertical reaction force, velocity of vertical ground reaction force to reach the maximum, time to stability in X and Y directions and resultant vector were calculated as postural control parameters. Also surface electromyography of transverse abdominal/int. oblique, vastus medialis, vastus lateralis, lateral gastrocnemius, and medial gastrocnemius muscles were recorded during landing. Motor control strategy were measured by similarity index and voluntary response index.

Results: There are significant difference between Genuvarum and Healthy subjects in motor control strategy (P<0.05).A significant difference are detected in postural control parameters between two groups (P<0.05).

Conclusion: Genuvarum deformity may be linked to altered quadriceps, abdominal and gastrocnemius muscles reciprocal co-activation patterns during landing task. In addition, may be affected voluntary motor control strategy in synergy concepts. Postural control is affected in these deformity and shock absorption may be reduced in parallel to increase of response vector and reduce of instability in landing task.

Keywords: Genuvarum; Postural Stability; Similarity index; Voluntary response index


sEMG: Surface Electromyography; SENIAM: Surface Electromyography for the Non-Invasive Assessment of Muscles; TA/IO: Transverse Abdominal/Int. Oblique; VM: Vastus Medialis; VL: Vastus Lateralis; MG: Medial Gastrocnemius; LG: Lateral Gastrocnemius; GRF: Ground Reaction Force; VGRF: Vertical GRF; TTP: Time to peak of VGRF; VGRFvel: Velocity of VGRF; TTS: Time to Stability; RV: Resultant Vector; SI: Similarity Index; VRI: Voluntary Response Index; RVi: Response Vector; PRVi: Prototype Response Vector.


Biological and mechanical approach for detection of impairments and treatments of knee lesions was reported previously [1-3]. Valgus deformity is very common in younger subjects and may to lead knee joint to osteoarthritis in elder ages.

The improvement of postural control can prevent the knee osteoarthritis and keen joint arthroplasty and side effect of infections.

There are multiple modalities that coordinate a complex activity, such as exteroceptive and proprioceptive sensations, motor control planning, muscle activities, joint biomechanics, postural stability. These coordination and redundancy are a complex process that are related to all of the degree of freedom of the above variable elements [4]. The effects of muscles on postural stability are very important and altered by motor control strategies and afferent pathway. Malalignment of biomechanic properties of joints, especially lower limbs can change, and variate afferents input to upper motor neuron [5].

Variation in motor control strategy in postural control may be increased by deformity in the knee joint such as knee genuvarum deformity by changes in muscles activities and motor control timings [6,7]. Normal postural stability is important aspect for maintaining quality of life in patients with knee genuvarum. When abnormalities occur in the joint, the visual or vestibular and other joints somatosensory systems, must control postural stability and therefore degree of freedom may increase. At these situations different muscle contractions work together and produce co-contraction instead of co-activation. Motor timings and muscles activity durations may increase, and postural stability may reduce [5,6].

A motor control deficit is a key factor for inducing patients with Genuvarum and a relationship may exist between changes in the normal timing of muscle activities (abdominal, quadriceps and gastrocnemius) of subjects with genuvarum [6,10,11].

It is clear that the patients’ motor control strategies and induces of synergy changed and analyses of above conditions are the focus of this paper.

The use of motor control parameters in assessment of postural stability in genuvarum is new approach and this study can be used for next researches and improve rehabilitation aims for patients with genuvarum.

Voluntary Response Index (VRI) has been used as measure of motor control to determine abnormal voluntary movements [12-18]. The VRI consists of two numeric values, one obtained from the total electrical activity of all muscles during a task (magnitude; Mag), and the other calculated from the Electromyography (EMG) distribution across the recorded muscles in comparison to specific prototype (Similarity Index; SI). This method analyses, quantitatively, the surface EMG activity of the related muscles during a given voluntary movement for assessment of voluntary motor control. In assessing.

Voluntary motor control assessment, the surface EMG activities of related muscles are analyzed during a given voluntary movement.

The aim of the present study is to evaluate postural stability and motor control variations in patients with genuvarum.


Twenty females with the age range of 20 to 30 years old participated in this study in two groups, 10 with healthy knee and 10 with Genuvarum deformity. Subjects would be excluded from the study if they had a history of neuromuscular and musculoskeletal disorders, surgery or fracture in the lower extremity over the past six months, and other lower limb abnormalities. The study was accomplished in the Biomechanics Laboratory at Rehabilitation Faculty of Shahid Beheshti University of Medical Sciences. Genuvarum deformity was measured by a camera capturing goniometer and MicroDicom viewer software (Figure 1) [6]. Different more than 11o between thigh and leg angle detected as Genuvarum [6,8-18].